111 research outputs found

    Impact of Imaging and Distance Perception in VR Immersive Visual Experience

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    Virtual reality (VR) headsets have evolved to include unprecedented viewing quality. Meanwhile, they have become lightweight, wireless, and low-cost, which has opened to new applications and a much wider audience. VR headsets can now provide users with greater understanding of events and accuracy of observation, making decision-making faster and more effective. However, the spread of immersive technologies has shown a slow take-up, with the adoption of virtual reality limited to a few applications, typically related to entertainment. This reluctance appears to be due to the often-necessary change of operating paradigm and some scepticism towards the "VR advantage". The need therefore arises to evaluate the contribution that a VR system can make to user performance, for example to monitoring and decision-making. This will help system designers understand when immersive technologies can be proposed to replace or complement standard display systems such as a desktop monitor. In parallel to the VR headsets evolution there has been that of 360 cameras, which are now capable to instantly acquire photographs and videos in stereoscopic 3D (S3D) modality, with very high resolutions. 360° images are innately suited to VR headsets, where the captured view can be observed and explored through the natural rotation of the head. Acquired views can even be experienced and navigated from the inside as they are captured. The combination of omnidirectional images and VR headsets has opened to a new way of creating immersive visual representations. We call it: photo-based VR. This represents a new methodology that combines traditional model-based rendering with high-quality omnidirectional texture-mapping. Photo-based VR is particularly suitable for applications related to remote visits and realistic scene reconstruction, useful for monitoring and surveillance systems, control panels and operator training. The presented PhD study investigates the potential of photo-based VR representations. It starts by evaluating the role of immersion and user’s performance in today's graphical visual experience, to then use it as a reference to develop and evaluate new photo-based VR solutions. With the current literature on photo-based VR experience and associated user performance being very limited, this study builds new knowledge from the proposed assessments. We conduct five user studies on a few representative applications examining how visual representations can be affected by system factors (camera and display related) and how it can influence human factors (such as realism, presence, and emotions). Particular attention is paid to realistic depth perception, to support which we develop target solutions for photo-based VR. They are intended to provide users with a correct perception of space dimension and objects size. We call it: true-dimensional visualization. The presented work contributes to unexplored fields including photo-based VR and true-dimensional visualization, offering immersive system designers a thorough comprehension of the benefits, potential, and type of applications in which these new methods can make the difference. This thesis manuscript and its findings have been partly presented in scientific publications. In particular, five conference papers on Springer and the IEEE symposia, [1], [2], [3], [4], [5], and one journal article in an IEEE periodical [6], have been published


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    Il progetto SPES prevede il bombardamento di un bersaglio in carburo di uranio con un fascio di protoni, in modo da generare, tramite reazione nucleare, specie radioattive all’interno del target. Le particelle radioattive generate vengono successivamente estratte, ionizzate, separate in massa ed accelerate come fascio di ioni radioattivo. Il presente lavoro di tesi ha riguardato lo studio di sicurezza di alcune unità dell'impianto SPES e si inserisce nell'ambito di una collaborazione di ricerca tra i Laboratori Nazionali di Legnaro ed il Dipartimento dell'Energia, sezione Nucleare, dell'Università degli Studi di Palermo. Tale attività ha comportato l'analisi sui componenti del sistema di produzione del vuoto e sul sistema di refrigerazione del target. In particolare l'attenzione è stata focalizzata sul Front-End dell'impianto SPES ovvero il complesso di apparecchiature adiacenti alla target chamber. Lo studio è stato effettuato attraverso l'utilizzo dell’analisi FMECA (Failure Mode, Effects and Criticality Analysis). Una prima fase dell'analisi ha riguardato lo studio dettagliato dei vari componenti che costituiscono l'impianto, dei loro modi di guasto e dei possibili effetti sul processo. I dati raccolti sono poi stati inseriti e successivamente analizzati tramite un database denominato Risk Analysis Database (RAD), messo a punto presso il Dipartimento dell'Energia dell'Università degli Studi di Palermo. Tramite tale analisi è stato possibile individuare le possibili deviazioni dal normale funzionamento che potrebbero condurre a situazioni incidentali di particolare interesse, individuare le procedure e i componenti che sono critici per la sicurezza dell'impianto e, nello stesso tempo, indicare o suggerire modifiche volte al raggiungimento di standard di sicurezza più elevati. A completamento di questo studio è stata condotta anche un’analisi termoidraulica sul sistema di refrigerazione del target avvalendosi del codice RELAP-3D 2.4.2 per valutare il comportamento dell'impianto durante i transitori incidentali e in tal senso si è preso come riferimento lo schema d’impianto del sistema di refrigerazione del target dell'impianto EXCYT dei laboratori LNS di Catania. L'analisi termoidraulica ha consentito di simulare l'andamento delle variabili d'impianto durante i transitori incidentali esaminati e di valutare la capacità intrinseca del circuito a far fronte a scostamenti dai parametri di progetto che potrebbero portare alla perdita dell'integrità strutturale

    SMCP: a Secure Mobile Crowdsensing Protocol for fog-based applications

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    The possibility of performing complex data analysis through sets of cooperating personal smart devices has recently encouraged the definition of new distributed computing paradigms. The general idea behind these approaches is to move early analysis towards the edge of the network, while relying on other intermediate (fog) or remote (cloud) devices for computations of increasing complexity. Unfortunately, because both of their distributed nature and high degree of modularity, edge-fog-cloud computing systems are particularly prone to cyber security attacks that can be performed against every element of the infrastructure. In order to address this issue, in this paper we present SMCP, a Secure Mobile Crowdsensing Protocol for fog-based applications that exploit lightweight encryption techniques that are particularly suited for low-power mobile edge devices. In order to assess the performance of the proposed security mechanisms, we consider as case study a distributed human activity recognition scenario in which machine learning algorithms are performed by users’ personal smart devices at the edge and fog layers. The functionalities provided by SMCP have been directly compared with two state-of-the-art security protocols. Results show that our approach allows to achieve a higher degree of security while maintaining a low computational cost

    SpADe: Multi-Stage Spam Account Detection for Online Social Networks

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    In recent years, Online Social Networks (OSNs) have radically changed the way people communicate. The most widely used platforms, such as Facebook, Youtube, and Instagram, claim more than one billion monthly active users each. Beyond these, news-oriented micro-blogging services, e.g., Twitter, are daily accessed by more than 120 million users sharing contents from all over the world. Unfortunately, legitimate users of the OSNs are mixed with malicious ones, which are interested in spreading unwanted, misleading, harmful, or discriminatory content. Spam detection in OSNs is generally approached by considering the characteristics of the account under analysis, its connection with the rest of the network, as well as data and metadata representing the content shared. However, obtaining all this information can be computationally expensive, or even unfeasible, on massive networks. Driven by these motivations, in this paper we propose SpADe, a multi-stage Spam Account Detection algorithm with reject option, whose purpose is to exploit less costly features at the early stages, while progressively extracting more complex information only for those accounts that are difficult to classify. Experimental evaluation shows the effectiveness of the proposed algorithm compared to single-stage approaches, which are much more complex in terms of features processing and classification time

    Bayesian Modeling for Differential Cryptanalysis of Block Ciphers: a DES instance

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    Encryption algorithms based on block ciphers are among the most widely adopted solutions for providing information security. Over the years, a variety of methods have been proposed to evaluate the robustness of these algorithms to different types of security attacks. One of the most effective analysis techniques is differential cryptanalysis, whose aim is to study how variations in the input propagate on the output. In this work we address the modeling of differential attacks to block cipher algorithms by defining a Bayesian framework that allows a probabilistic estimation of the secret key. In order to prove the validity of the proposed approach, we present as case study a differential attack to the Data Encryption Standard (DES) which, despite being one of the methods that has been most thoroughly analyzed, is still of great interest to the scientific community since its vulnerabilities may have implications on other ciphers

    RELAP5 simulation of two-phase flow experiments in vertical helical tubes

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    In the framework of the studies concerning the thermalfluid dynamic phenomena in helicoidal pipes of the innovative nuclear reactor IRIS steam generators, the Department of Nuclear Engineering of the University of Palermo in collaboration with the Politecnico di Torino Department of Energetics has been engaged in a work aimed to adapt, by implementing new suitable models, RELAP5/mod3.2.2β code to simulate the thermalfluid-dynamics and geometries such as the ones involved in helicoidal pipes. In fact this code is based on one-dimensional thermal-hydraulic relationships and presents limitations to model complicated geometry such as helicoidal pipes. Therefore the code was improved with additional correlations that are valid for two-phase flow and allow to overcome the drawbacks. The validation work of the models that were added is based on the experimental data carried out at the Politecnico di Torino Department of Energetics. In this paper it will be shown that the so modified RELAP5 code allows to represent adequately the experimental data

    Your Friends Mention It. What About Visiting It? A Mobile Social-Based Sightseeing Application

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    In this short poster paper, we present an application for suggesting attractions to be visited by users, based on social signal processing technique

    Photorealistic True-Dimensional Visualization of Remote Panoramic Views for VR Headsets

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    © 2023 IEEE. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/Virtual Reality headsets have evolved to include unprecedented display quality. Meantime, they have become light-weight, wireless and low-cost, which has opened to new applications and a much wider audience. Photo-based omnidirectional imaging has also developed, becoming directly exploitable for VR, with their combination proven suitable for: remote visits and realistic scene reconstruction, operator’s training and control panels, surveillance and e-tourism. There is however a limited amount of scientific work assessing VR experience and user’s performance in photo-based environment representations. This paper focuses on assessing the effect of photographic realism in VR when observing real places through a VR headset, for two different pixel-densities of the display, environment types and familiarity levels. Our comparison relies on the observation of static three-dimensional and omnidirectional photorealistic views of environments. The aim is to gain an insight about how photographic texture can affect perceived realness, sense of presence and provoked emotions, as well as perception of image-lighting and actual space dimension (true-dimension). Two user studies are conducted based on subjective rating and measurements given by users to a number of display and human factors. The display pixel-density affected the perceived image-lighting and prevailed over better lighting specs. The environment illumination and distance to objects generally played a stronger role than display. The environment affected the perceived image-lighting, spatial presence, depth impression and specific emotions. Distances to a set of objects were generally accurately estimated. Place familiarity enhanced perceived realism and presence. They confirmed some previous studies, but also introduced new elements.Peer reviewe

    The Evolving Scenario in the Assessment of Radiological Response for Hepatocellular Carcinoma in the Era of Immunotherapy: Strengths and Weaknesses of Surrogate Endpoints

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    Hepatocellular carcinoma (HCC) is a challenging malignancy characterised by clinical and biological heterogeneity, independent of the stage. Despite the application of surveillance programs, a substantial proportion of patients are diagnosed at advanced stages when curative treatments are no longer available. The landscape of systemic therapies has been rapidly growing over the last decade, and the advent of immune-checkpoint inhibitors (ICIs) has changed the paradigm of systemic treatments. The coexistence of the tumour with underlying cirrhosis exposes patients with HCC to competing events related to tumour progression and/or hepatic decompensation. Therefore, it is relevant to adopt proper clinical endpoints to assess the extent of treatment benefit. While overall survival (OS) is the most accepted endpoint for phase III randomised controlled trials (RCTs) and drug approval, it is affected by many limitations. To overcome these limits, several clinical and radiological outcomes have been used. For instance, progression-free survival (PFS) is a useful endpoint to evaluate the benefit of sequential treatments, since it is not influenced by post-progression treatments, unlike OS. Moreover, radiological endpoints such as time to progression (TTP) and objective response rate (ORR) are frequently adopted. Nevertheless, the surrogacy between these endpoints and OS in the setting of unresectable HCC (uHCC) remains uncertain. Since most of the surrogate endpoints are radiology-based (e.g., PFS, TTP, ORR), the use of standardised tools is crucial for the evaluation of radiological response. The optimal way to assess the radiological response has been widely debated, and many criteria have been proposed over the years. Furthermore, none of the criteria have been validated for immunotherapy in advanced HCC. The coexistence of the underlying chronic liver disease and the access to several lines of treatments highlight the urgent need to capture early clinical benefit and the need for standardised radiological criteria to assess cancer response when using ICIs in mono- or combination therapies. Here, we review the most commonly used clinical and radiological endpoints for trial design, as well as their surrogacy with OS. We also review the criteria for radiological response to treatments for HCC, analysing the major issues and the potential future perspectives
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